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R. A. HEISING v SYSTEM FOR THE TRANSMISSION 0F INTELLIGENCE.

' APPLICATION mm JULY16, 191s.

Reissued Oct. 26, 1920.

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' Ray/77 andA/ie/s/ny by M Al Original No. 1,199,180, dated September26, 1916, Serial No. 55,048; filed October reissue filed July 16, 1918.Serial No. 245,243.

UNIT El) STATES; v PATENT omen.

RAYMOND a. imrsme, or EAST ORANGE, NEW JERSEY, ASSIGNOR,

MENTS, T0 AMERICAN TELEPHONE & TELEGRAPH COMPANY,

NEW YORK.

T 0 all whom it may concern:

Be it known that I RAYMOND A. HEISING,-

a citizen of the United States, residing at East Orange, in the countyof Essex and State of New Jersey, have invented certain new and usefulImprovements in Systems for the Transmission of Intelligence, of whichthe following is a full, clear, concise, and exact description.

This invention relates to improvements in the art of transmittingsignals by means of high frequency electric waves.

ts object is to provide means for modulating the amplitude of ahigh-frequency wave in accordance with the wave form of a low-frequencysignal to' be transmitted. This object is accomplished by impressingupon one part of the divided input circuit of a thermionic amplifier ahigh frequency voltage, and upon the other part of'said input clrcuit avoltage having the wave form of the signal to be transmitted. As a result of this, there appear in the output circuit of the amplifier, underproper conditions, amplified and modulated high fre quency currentswhich may be used to supply power to an antenna or other circuit fromwhich the signal is to be transmitted.

The possibility of so producing a modulated high-frequency currentdepends upon the fact that the amplifying power of the thermionicrepeater depends upon, and increases with, the voltage impressed uponits input terminals. If, therefore, a variable voltage, corresponding tothe signals to be sent, is impressed upon one part of the input circuit,and if the high-frequency alternating voltage is impressed upon anotherpart, the high-frequency power appearing in the output circuit will varyin accordance with the low-frequency signal voltage. In

thus applying these two voltages, it is es-" maintained even if thecondition is violated,-

but the quality is then somewhat impaired. The circuitgarrangement whichhas been BY mis w ASSIGN- A conro tarron or or INTELLIGENCE.

9, 1915. Application tor found by experiment to be most desirable 1sthat shown in the drawing, which represents a preferred form of thisinvention.

In that drawing, 1 represents any suitable generator of high-frequencypower. It need not have'a large power capacity, since it is required tofurnish but a small high-frequency voltage. By means of t e transformer2, the electromotive force eveloped by generator 1 is impressed upon 3,of, the divided input circuit of a thermionic amplifier 4, whose otherelements are a heated cathode 5, an anode 6, and a second grid element7.

8 represents a microphone, and 9 a battery by means of which it issupplied with direct primary 7 circuit contains the microphone, providesthat a signal voltage produced in one grid,

current. The transformer 10, whose' Specification of Reissued LettersPatent. Reisgfled 0013.26, 1920,

the microphone circuit shall be impressed upon the second input element7 of the am-.

11, 11 are batteries whose insure that the electrodes 3 always be atnegative potentials with respect to the filament 5. Under thesecircumstances no electrons can pass from the filament 5 to either inputelectrode, and

objects are to therefore practically no current is'taken by the inputcircuit.

12 is another battery which maintains the space current in the amplifierbetween anode 6 and cathode 5. The output circuit of this amplifiercontains the coil 13, to which is coupled ano her coil 14, which, incombina 'tion with condenser 15, forms a tuned circuit whosefrequency-may .be adjusted to that of the wave to be transmitted. Thehigh non-inductive resistance 16 is preferably'placed in shunt tothecondenser 15, its object being to adjust the sharpness of tuningofthe resonant circuit,and also to insure thatthe input circuits of theamplifiers, next to be described, im edance to incoming waves.

he amplifiers 17 are arranged in parallel and have their input circuitsconnected across the terminals of the resonant circuit 14, 15,- thecommon output eircuitof these amplifiers including the coil 18. Theobject of these amplifiers is to produce, in the outputcircuit, .avoltage. considerably larger and 7 shall shall offer a definite thanthat appearing over their input circuits, and it is not essential thatthe power output of this set shall be large. The resonant circuit 19,20, also tuned to the frequency to be transmitted, is coupled to thecoil 18. .The input circuits of a number of amplifiers 22, arranged inparallel, are connected to the terminals of this second resonantcircuit. The resistance 21 is added because it has been found to rendermore stable the o eration of the. amplifiers 22. These ampli ers areespecially designed to produce in their output circuits high currents,rather than high effective alternating voltages, and therefore thecombination of amplifiers 17 with amplifiers 22 serves to increase boththe voltage and current components of the power a pearing in the outputcircuit of the mo ulator element. In practice it has been found possibleto employ as many as 500 amplifiers of the ty e 22. The common outputcircuit of ampl fiers 22 is finally coupled, by means of transformer 23,to the radiating antenna 24. Any suitable receiving station may be usedto receive the signals thus transmitted.

The operation of the modulating amplifier 4 is as follows:High-frequency voltages impressed upon the grid 3 from the generator 1are, in the absence of an electromotive force due to microphone 8,simply repeated in enlarged form as variations of current in the outputcircuit. When, however, an electromotive force of the si a1 wave form isimpressed upon the grid the effect of the signaling-voltage is to changethe amplifying power of the repeater 4c, and consequently to change alsothe amplitude of the high-frequency current variations in its outputcircuit. A modulated high-frequency current is therefor produced in thecoil 13, and its effects are transmitted to antenna 24 by means of theintermediate apparatus, whose operation has already been describedsufiiciently in detail. Y Although this invention is shown as aplied tothe transmission of radio signals, it-

is obvious that the mere substitution of a wire circuit, for example atelephone line, for the antenna 24, will permit the use of this s stemfor the transmission of modulatedigh-frequency waves over wire lines,and I therefore desire to include that application as apart of myinvention. It is also obvious that departures may be made from theparticular circuit arrangement shown in the drawing.

What is claimed is:

1. Anelectron discharge device comprisreceiving element, and twoimpedance controlling elementsfor substantially independently varyingthe impedance presented to an electron stream between said electronemitting element-and said electron receiving element.

2. An electron discharge device comprising an electron emitting element,an electron receiving element, two impedance controlling elements, andmeans for independently varying the potentials of said impedancecathode, an anode, means for varying at a high frequency rate, theimpedance offered to an electron stream between said cathode and anode,and means substantially independent of said first named means forvarying said impedance at a signaling frequency rate.

5. modulator comprising an electron discharge device having a cathode,an anode.

and two electron discharge control elements, an external source of highfrequency waves, means for applying high frequency potential variationsfrom said source to one of said control elements, and means for applyingsignaling frequency potential variations to the other of said controlelements to vary the impedance presented to the same electron stream.

6. A modulator comprising an electron discharge device having an inputcircuit and an output circuit, means for impressing a high frequencyelectromotive force upon said input circuit, and means substantiallyindependent of said input circuit for varying the impedance of saiddevice in accordance with signals, whereby waves of said high frequencyvarying in amplitude in accordai'ice with said signals are produced insaid output circuit, and a transmission circuit connected to said outputcircuit for receiving therefrom and transmitting said signal modulatedWaves.

A modulator comprising an electron discharge device having an inputcircuit and an output circuit, means for impressing a high frequencyelectromotive force upon said input circuit, and means substantiallyindependent of said input circuit and said ing an electron emittingelement, an electron output circuit for varying the impedance of saiddevice in accordance with signals, whereby waves of said high frequencyvarying in amplitude in accordance with said signals are produced insaid output circuit,

. quency varying and a transmission circuit connected to said outputcircuit for receiving therefrom and transmittin said signal modulatedwaves.

8. A modulator comprising an electron discharge device having an inputcircuit and an output circuit, means for impressing a high frequencyelectromotive force upon said input circuit, and means substantial-1yindependent of said input circuit for varying the impedance of saiddevice in accordance with audio frequency variations, whereby waves ofsaid high frequency varying in amplitude in accordance with said audiofrequency variations are produced in said output circuit, and atransmission cir-' cuit connected to said output circuit for re ceivingtherefromand transmitting said modulated high frequency waves.

9. A modulator comprising an electron discharge device having an inputcircuit and an output circuit, means for impressing a high frequencyelectromotive force upon said input circuit, and means substantiallyindependent of said input circuit for varying the impedance of saiddevice in accordance with oscillations of a different frequency,whereby-waves of said high frein amplitude in accordance with saiddifferent frequency oscillations are produced in said output circuit,and a transmission circuit connected to said output circuit forreceiving therefrom and transmitting said modulated high frequencywaves.

10. The combination in a radio transmission system, of an antenna, asource of highfrequency waves, a source of waves of signaling frequency,a thermionic repeater having an output circuit and a divided'inputcircuit, the two parts of said input circuit being connectedrespectively to said sources of high-frequency waves and oflow-frequency waves, of amplifying means whereby the modulatedhigh-frequency waves in the output circuit of said repeater maybe'further increased in power, and a means for impressing such augmentedpower upon said antenna.

11. In a system for the transmission of signals by means of modulatedhigh-fro quency waves, a circuit, a thermionic amplifier having anoutput circuit, connected to said first mentioned circuit, and a dividedinput circuit; means electrically remote from said amplifier and itsother .circuits for impressing high-frequency electric oscillations uponone part of said divided circuit, and means for impressing impulses ofsignaling frequency upon the other part of said divided circuit.

12. In a. system for the transmission of signals by means of modulatedhigh-frequency waves, a circuit, a source of impulses of signalingfrequency, a source of oscillations of high-frequency, and a thermionicone of the grlds and audio amplifier having two grid elements, one ofsaid elements being connected to said source of impulses, the other tosaid source of oscillations, and the output' circuit of said amplifierbeing so connected as to transfer power to said first mentioned circuit.

13. A thermionic amplifier having an input circuit and an outputcircuit, means for impressing an alternating electromotive force uponsaid input circuit, and means substantially independent of said inputcircuit for varying the amplifying power of said amplifier in accordancewith signal variations.

14. A thermionic put circuit and twoinput circuits, external means forproducing and impressing a varying electro-motive force upon one of saidinput circuits, and means associated with the other of said inputcircuits for varying the amplifying power of'said amplifier inaccordance withsignals.

15. The method of modulation which comprises subjecting an electronstream to the action of two variable impedances, each of which has amagnitude independent of that of said electron stream, one of whichimpedances varies cyclically and the other of which varies in accordancewith signals.

16. The method of operating an electron discharge device comprising acathode, an anode, and two grids, which consists in impeding the sameelectron strain by applying radio frequency potential variations tofrequency po tential variations .to the other, said potential variationsbeing independent of each other.

17. The method of operating an electron discharge device comprisingsubjecting a single electron stream to the action of a plurality ofvariable impedanceseach of which has a magnitude substantiallyindependent of said electron stream and each of which varies inaccordance with an alternating electromotive force individual thereto.

18. The method of operating an electron discharge device comprisingsubjecting a single electron stream to the action of a plurality ofsubstantially independent impedances and causing said impedances to varyindependently of each other.

19. The combination with an amplifier having the property of variablyamplifying in accordance with the energy impressed thereon, of means forsimultaneously independently impressing high frequency waves and lowfrequency waves upon said amplifier, the amplitude of said highfrequency waves being less than the amplitude of said frequency waves.

20. In combination, a discharge device having a cathode and an anode, asource of current for producing an electric discharge stream betweensaid cathode and anode, and

low

amplifier having an out-- a plurality of variable impedance elements soassociated with said device as to present substantially independentlyvarying impedances to said stream between said cathode and said anode.

21. In combination, an electron discharge device having an outputcircuit, a second electron discharge device having an input circuit, atransformer connecting said circuits, a capacity element forming a tunedcircuit with the secondary winding of said transformer, and a resistancein shunt to said capacity element.

22. In combination, an electron discharge device hzving an outputcircuit, a second electron discharge device having an input circuit,means comprising an inductance associating said circuits, and a capacityelement and a resistance element in parallel thereto and forming a tunedcircuit therewith. v

23. In combination an electron discharge device having an outputcircuit, a second electron discharge device having an input circuit,said circuits being coupled by a transformer, a capacity element forminga tuned circuit with one winding-0f said transformer, and meanscomprising a resistance in shunt to said capacity element connectedthereto to adjust the sharpness of tuning of said circuit.

' 24. In combination an electron discharge device havin an outputcircuit, a second electron disc arg'e device having an input circuit,and means comprising a transformer for coupling said circuits, saidtransformer having one winding shunted by a capacity element and by aresistance element.

25. A modulator! comprising a discharge device having a cathode and ananode, a source of current for producing an electric discharge streambetween said cathode and anode, and a plurality of variable impedanceelements so associated with said device as to present substantiallyindependently varying impedances to said stream between said cathode andsaid anode.

In witness whereof, I hereunto subscribe my name this 1st da of July,1918.

RAY 0ND A. HEIS'ING.

